The sealing surface of the valve is often corroded, eroded, and worn by the medium, making it a vulnerable component of the valve. For example, automatic valves such as pneumatic ball valves and electric butterfly valves have frequent opening and closing and fast opening and closing speeds, and their quality directly affects the service life of the valve. The basic requirement for valve sealing surface is to ensure safe and reliable sealing of the valve under specified working conditions. Therefore, the material of the valve sealing surface should have the following characteristics:

(1) Good sealing performance, that is, the sealing surface should be able to effectively prevent the leakage of the medium;

(2) A certain strength, under the action of medium pressure difference, the sealing surface should be able to withstand the sealing specific pressure value formed by it;

(3) Corrosion resistance, the sealing surface should have strong corrosion resistance that is suitable for the design requirements under the long-term action of corrosive media and stress;

(4) Resistance to scratches, valve sealing pairs are all dynamic seals, and there is friction between the sealing pairs during the opening and closing process

(5) Corrosion resistance, the sealing surface should be able to resist the erosion of high-speed media and the collision of solid particles;

(6) Good thermal stability, the sealing surface should have sufficient strength and antioxidant capacity at high temperatures, and good resistance to cold brittleness at low temperatures;

(7) Good processing performance, easy manufacturing and maintenance, universal components for valve function, ensuring economic value.

The usage conditions and selection principles of valve sealing surface materials are divided into two categories: metal and non-metal. The applicable conditions for commonly used materials are as follows:

(1) Rubber. Generally used for sealing surfaces of low-pressure soft sealed gate valves, diaphragm valves, butterfly valves, check valves, and other valves.

(2) Plastic. Plastics used for sealing surfaces include nylon and polytetrafluoroethylene, which have good corrosion resistance and low friction coefficient. Soft sealed ball valves are widely used.

(3) Babbitt alloy. Also known as bearing alloy, it has good corrosion resistance and good running in ability. Suitable for sealing surfaces of ammonia shut-off valves with low pressure and temperatures ranging from -70 to 150 ℃

(4) Copper alloy. It has good wear resistance and a certain degree of heat resistance. Suitable for globe valves, cast iron gate valves, and check valves, generally used for low pressure, water and steam with temperatures not exceeding 200 ℃.

(5) Chromium nickel stainless steel. It has good corrosion resistance, erosion resistance, and heat resistance. Suitable for media such as steam nitric acid.

(6) Chromium stainless steel. It has good corrosion resistance and is usually used on valves for high pressure, oil products with a temperature not exceeding 450 ℃, water vapor, and other media.

(7) High chromium overlay welded steel. Has good corrosion resistance and work hardening performance, suitable for high-pressure, high-temperature oil products, steam and other media.

(8) Nitrided steel. It has good corrosion resistance and scratch resistance, and is usually used on gate valves in thermal power plants. The ball of hard sealed ball valves can also choose this material.

(9) Hard alloy. It has good comprehensive properties such as corrosion resistance, erosion resistance, and scratch resistance, and a long service life, making it an ideal sealing material. Commonly used tungsten diamond based alloy and diamond based alloy welding rods can be used to produce ultra-high pressure and ultra-high temperature sealing surfaces, suitable for media such as oil, gas, and hydrogen.

(10) Spray welding of alloys. There are cobalt based alloys, nickel based alloys, which have good corrosion resistance, wear resistance, and other properties.

In order to ensure the safety and reliability of the valve sealing surface, the selection of sealing surface materials must be determined based on specific working conditions. If the medium has strong corrosiveness, when selecting materials, the corrosion performance should be met first, and then other performance requirements should be met.